Making a Duck Pond Bio-Filter
First you need a large container. Our pond is 110 gallons, so we've got roughly a 2 to 1 ratio here with a 50 gallon Rubbermaid container. This is freakishly large for koi but hopefully about right for 9 ducks. Install a standard shower drain about 3/4 from the bottom:
Cut a hole in the top to allow for the intake riser plumbing, this is where dirty water gets pumped from the pond into the bottom of the bio-filter:
The internal plumbing is pretty simple - two lengths, one T, two right angles (set in opposite directions), a long piece that comes out the top. Install a grid roughly 1/4 from the bottom to hold the filter media above the intake plumbing, you'll need to cut a hole to allow the internal plumbing:
Fill to the top with filter media, in our case roughly $30 of sponges from the Dollar Store:
The riser plumbing piece. It looks a bit like a periscope:
With the top on:
Then, place the bio-filter near your Pond and hook up the internal pond pump to the riser intake plumbing and allow the long shower drain to flow clean water back into your pond. Here's a little movie of our ducks enjoying their pond.